Question: Simplify the following expression: $r = \dfrac{-7a}{10} + \dfrac{a}{10}$
Explanation: Since the expressions have the same denominator we simply combine the numerators: $r = \dfrac{-7a + a}{10}$ Combine like terms: $r = \dfrac{-6a}{10}$ Simplify by dividing numerator and denominator by 2: $r = \dfrac{-3a}{5}$